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Sen-yeu Yang - One of the best experts on this subject based on the ideXlab platform.

  • a study on the micro injection Molding of multi Cavity ultra thin parts
    Polymers for Advanced Technologies, 2011
    Co-Authors: Sen-yeu Yang, S C Nia, S T Huang, Yungchu Weng
    Abstract:

    In this study, we report the micro-injection Molding of ultra-thin parts (100, 250, and 500 µm). The results show that the flow resistance increases as the Cavity becomes thinner. The melt front is not symmetric when filling a four-Cavity ultra-thin part and filling the eight-Cavity Mold under a low temperature. If we increase the Mold temperature or Cavity thickness, the melt front becomes symmetric. Finally, we construct the operation windows of Molding for three kinds of plastics (PS, PMMA, PC) and provide a Molding range based on Mold temperature and injections speed. Meanwhile, the relationship between the thickness and the operation windows are also investigated. The thinner the Cavity is, the smaller the operation window is. We need to increase the injection speed significantly for Molding the ultra-thin parts with micro-features on both surfaces which are 60 µm in thickness. Furthermore, we succeed in Molding 30 µm ultra-thin parts in this experiment. Copyright © 2009 John Wiley & Sons, Ltd.

  • Improving Flow Balance during Filling a Multi-Cavity Mold with Modified Runner Systems
    International Polymer Processing, 2008
    Co-Authors: Tzu Chien Huang, Po-hsun Huang, Sen-yeu Yang
    Abstract:

    Abstract Multi-Cavity injection Molding has been regarded as low cost mass-production method for producing plastic products such as optical elements. However, the flow imbalance during filling a multi-Cavity Mold using symmetrical runner system is a serious problem. This paper is devoted to improving the flow balance by modifying the runner system design. For this purpose, four eight-Cavity Molds with four modified symmetrical runner systems are designed, constructed and tested. They are tapering H-type runners, pinned H-type runners, curved A runners, and curved B runners. The flow imbalance in each runner system is observed and measured with the aid of short-shot experiments. The experimental results indicate that the tapering H-type runner system can improve flow balance. The pinned H-type runner system fails to improve flow balance. The curved A and B runner system can reverse the imbalance trend, but the stability of the curved systems is poor at high melt temperature.

  • Study on Flow Imbalance during Filling a Multi-Cavity Mold Using a H-type Runners
    Key Engineering Materials, 2007
    Co-Authors: Sen-yeu Yang, Tzu Chien Huang, Po-hsun Huang
    Abstract:

    This study reports the experimental investigation on the flow imbalance phenomena during filling symmetrical multi-Cavity in injection Molding of optic elements. There are two aspects in this study: First, the flow imbalance in the eight-Cavity Mold with normal H-type symmetric runners were observed and measured with aid of short-shot experiments. Second, the effects of three processing conditions including injection speed, melt temperature and Mold temperature on flow imbalance were investigated. Flow imbalances are consistently observed and quantitatively measured. The results have shown that proper injection speed, high melt and high Mold temperature can reduce the flow imbalance.

  • Effects of cooling time and Mold temperature on quality of Moldings with precision contour
    Advances in Polymer Technology, 1996
    Co-Authors: Sen-yeu Yang, L. Lien
    Abstract:

    Injection Molding is now used to Mold plastic parts with precision contours such as lenses. Cooling conditions have critical effects on the quality and productivity of such precision parts. This article is devoted to investigate the effects of Mold temperature and cooling time on quality. A two-Cavity Mold for Molding convex lenses with square-looped cooling channels was used. Samples Molded with different Mold temperatures and cooling times were collected, and their contour conformity to those of the Cavity was evaluated. Contour errors were defined. The correlation between Mold temperature and cooling time and contour errors was analyzed. It has been found that for a given Mold temperature, two critical cooling times can be defined at which the thermal and rigidity states pass through a transition. Most dramatic improvements in part conformity occur around such critical points. © 1996 John Wiley & Sons, Inc.

Hidetoshi Yokoi - One of the best experts on this subject based on the ideXlab platform.

  • A Study on Influence of Resin Temperature on Filling Balance of Multi-Cavity Molds
    Advanced Materials Research, 2009
    Co-Authors: Jing Bo Chen, Changyu Shen, Hidetoshi Yokoi
    Abstract:

    Filling imbalance for PP, long GF-PP, elastomer PC and GF-PC in a multi-Cavity Mold with a geometrically balanced runner is investigated by using the visualization glass-inserted injection Mold and infrared thermometers, through visualizing the flow behavior of the melt in the runner and Cavity and measuring the melt temperature near the Cavity entrance simultaneously. In addition, velocity distribution in the secondary runner for PP and elastomer is also determined by use of marker tracers in order to further investigate the mechanism of filling balance. The results show that the degree of filling imbalance depends on the velocity difference of the upper and lower melt and its development in the secondary runner during the filling process. The melt viscosity difference in the primary runner dominate the melt velocity difference in the secondary runner., and the viscosity difference depends on the temperature difference and viscosity sensitivity to temperature and shear rate. The development of the velocity difference of the upper and lower melt in the secondary runner depends on the melt viscoelastic property and the runner wall condition.

  • Measurement of Ultra High-Speed Injection Molding Process Using Thin Bar-Flow Cavity
    Seikei-kakou, 2005
    Co-Authors: Shigeru Hasegawa, Kim Wookyu, Hidetoshi Yokoi
    Abstract:

    In this study, we developed a thin-walled bar-flow Cavity Mold (Cavity thickness: 0.5mm) in order to understand the influence of residual gas inside the Cavity on the flow length and appearance during ultra high-speed injection Molding of polypropylene (PP) and liquid crystal polymer (LCP). Both the resin flow and the internal gas pressure were simultaneously measured. The results of the effects of gas-venting on the flow length and blister generation of the LCP and PP Molded part are summarized as follows:1) The flow length of PP and LCP Molded samples increased with increasing screw injection speed (injection rate), but the flow length did not differ between natural exhaust (with gasvent) and forced exhaust (with vacuum-pumping).2) After heat treatment, numerous blisters were found in the LCP Molded samples during high injection rates under natural exhaust, but not under forced exhaust even at ultra high-speed.3) The results suggested that blisters generated from residual gases trapped in the resin due to the jetting phenomenon inside the sprue during ultra high-speed filling.

Shuang-chen Ruan - One of the best experts on this subject based on the ideXlab platform.

  • Laminated fabrication of 3D queue micro-electrode and its application in micro-EDM
    The International Journal of Advanced Manufacturing Technology, 2015
    Co-Authors: Jian-guo Lei, Rong Cheng, Shuang-chen Ruan, Zhen-long Wang
    Abstract:

    3D micro-electrode used in micro electrical discharge machining (micro-EDM) is difficult to be fabricated. Based on laminated object manufacturing (LOM) process, this paper superimposed multilayer 2D micro-structures together to fit out 3D micro-electrode and applied it in micro-EDM to process 3D micro-Cavity Mold. Firstly, 100-μm-thick Cu foils were cut by wire-electrical discharge machining (WEDM) to obtain multilayer 2D micro-structures, and then these 2D micro-structures were connected together to fit out 3D micro-electrode through vacuum pressure thermal diffusion welding. Secondly, under the effect of 80-V voltage, 0.2-MHz pulse frequency, 800-ns pulse width, and 4200-ns pulse interval, the 3D micro-electrode was applied in micro-EDM and 3D micro-Cavity Mold with high surface quality was obtained. Thirdly, in order to reduce the adverse impact of electrode wear on machining precision of 3D micro-Cavity Mold, 3D queue micro-electrode was used to process the same 3D micro-Cavity Mold, in which the first electrode is for rough machining and the others for fine machining. Finally, based on the above studies, two kinds of 3D queue micro-electrodes were fabricated, and the 3D micro-Cavity Molds with surface roughness Ra = 0.48 μm were obtained through micro-EDM. Compared with the scanning 3D micro-EDM process, the 3D micro-Cavity Mold can be obtained through up and down reciprocating method of the 3D queue micro-electrode, featuring simple machining process and high efficiency.

  • research on micro electric resistance slip welding of copper electrode during the fabrication of 3d metal micro Mold
    Journal of Materials Processing Technology, 2013
    Co-Authors: Bin Xu, Xiaoyu Wu, Feng Gong, Chenlin Du, Shuang-chen Ruan
    Abstract:

    a b s t r a c t 3D micro-Mold fabricated by the micro double-staged laminated object manufacturing process (micro- DLOM) is formed via stacking and fitting of multi-layer 2D micro-structures. The connection of 2D micro-structures is related to forming accuracy and mechanical properties of 3D micro-Mold. In this research, micro-electric resistance slip welding of copper electrodes was proposed to connect multi- layer 2D micro-structures. Firstly, the proper process parameters of slip welding were obtained through the welding experiment, and the temperature field of micro-electric resistance slip welding under such process parameters was simulated. Secondly, deposition effect of the copper bar electrode produced during slip welding was studied and the study results show that the copper element deposited in the slip welding area decreases as the surface roughness of copper electrode decreases. Finally, based on the above research, a square micro-Cavity Mold with micro-channel, a circular micro-Cavity Mold with cross keyway and micro gear Cavity Mold with two-stage steps were welded by the micro-electric resistance slip welding. © 2013 Elsevier B.V. All rights reserved.

Yungchu Weng - One of the best experts on this subject based on the ideXlab platform.

  • a study on the micro injection Molding of multi Cavity ultra thin parts
    Polymers for Advanced Technologies, 2011
    Co-Authors: Sen-yeu Yang, S C Nia, S T Huang, Yungchu Weng
    Abstract:

    In this study, we report the micro-injection Molding of ultra-thin parts (100, 250, and 500 µm). The results show that the flow resistance increases as the Cavity becomes thinner. The melt front is not symmetric when filling a four-Cavity ultra-thin part and filling the eight-Cavity Mold under a low temperature. If we increase the Mold temperature or Cavity thickness, the melt front becomes symmetric. Finally, we construct the operation windows of Molding for three kinds of plastics (PS, PMMA, PC) and provide a Molding range based on Mold temperature and injections speed. Meanwhile, the relationship between the thickness and the operation windows are also investigated. The thinner the Cavity is, the smaller the operation window is. We need to increase the injection speed significantly for Molding the ultra-thin parts with micro-features on both surfaces which are 60 µm in thickness. Furthermore, we succeed in Molding 30 µm ultra-thin parts in this experiment. Copyright © 2009 John Wiley & Sons, Ltd.

Weng Poo Kang - One of the best experts on this subject based on the ideXlab platform.

  • Physical characterization of diamond pyramidal microtip emitters
    Journal of Vacuum Science & Technology B, 1997
    Co-Authors: Weng Poo Kang, Jimmy L. Davidson, M.a. George, I. Milosavljevic, David V. Kerns
    Abstract:

    Micropatterned diamond pyramidal tips have been demonstrated to have high emission current. This article presents in great detail the physical characterizations that have proceeded to characterize the topology, morphology, and microstructure of these diamond microtips using transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning tunneling microscopy (STM), and Raman spectroscopy. The results show that the diamond microtips are indeed a polycrystalline diamond structure as evidenced by Raman spectroscopy and diffraction analysis of the TEM. AFM and STM results provide detail information as to the surface and tip shape of the diamond emitters. AFM/STM observations suggest a nucleation and growth process whereby the matter in which chemical vapor deposition diamond nucleates on the planar top surface of the tip substrate is distinct and different from the way the diamond grows in the Cavity “Mold.” Likewise, the TEM results contrast the diamond microstructure in the field area with th...

  • Physical characterization of diamond pyramidal microtip emitters
    9th International Vacuum Microelectronics Conference, 1996
    Co-Authors: Weng Poo Kang, Jimmy L. Davidson, M.a. George, I. Milosavljevic, James E. Wittig, M. Howell, David V. Kerns
    Abstract:

    Micro patterned diamond pyramidal tips have demonstrated high emission current. This paper presents the physical analyses that have proceeded to characterize the topology, morphology and microstructure of these diamond microtips using transmission electron microscopy, atomic force microscopy, scanning tunneling microscopy, and Raman spectroscopy. The results show that the diamond microtips are indeed a polycrystalline diamond structure as evidenced by Raman spectroscopy and diffraction analysis of the TEM. AFM and STM results provide detailed information as to the surface and tip shape of the diamond emitters. AFM/STM observations suggest a nucleation and growth process whereby the manner in which CVD diamond nucleates on the planar top surface of the tip substrate is distinct and different from the way the diamond grows in the Cavity "Mold". Further, the TEM results contrast the diamond microstructure in the field area with that of the tip where distinct differences are observed.

  • A novel low-field electron-emission polycrystalline diamond microtip array for sensor applications
    Sensors and Actuators A-physical, 1996
    Co-Authors: Weng Poo Kang, Jimmy L. Davidson, D. L. Kinser, D.v. Kerns
    Abstract:

    Abstract Electron field emission from an array of patterned pyramids of polycrystalline diamond has been investigated for microsensor applications. Selective deposition and Molding of a polycrystalline diamond film in a silicon Cavity Mold and subsequent creation of a freestanding polycrystalline diamond diaphragm with diamond pyramidal microtips has been achieved. The processing techniques are compatible with IC and micromachining technologies. High current emission from the patterned diamond microtip arrays is obtained at low electric fields. Field emission for these diamond microtips exhibits significant enhancement in total emission current compared to silicon emitters. Moreover, field emission from patterned polycrystalline diamond pyramidal-tip arrays is unique in that the applied field is found to be lower than the required for emission from S 1 , Ge, GaAs, and metal surfaces. The findings suggest the potential use of diamond-based field-emitter arrays in microsensors such as pressure sensors, accelerometers, and tactile sensors.

  • A Novel Low Field Electron Emission Polyerystalline Diamond Microtip Arrays For Sensor Applications
    Proceedings of the International Solid-State Sensors and Actuators Conference - TRANSDUCERS '95, 1995
    Co-Authors: Weng Poo Kang, Jimmy L. Davidson, D. L. Kinser, D.v. Kerns
    Abstract:

    Electron field emission from an array of patterned pyramids of polyerystalline diamond for microsensor applications has been investigated. Selective deposition and Molding of polycrystalline diamond film in a silicon Cavity Mold and subsequent creation of free standing polycrystalline diamond diaphragm with diamond pyramidal-microtips has been achieved.